Roofs of buildings are typically formed of multiple materials and surfaces designed to maintain a barrier between the interior of the structure and the weather. One of the most pervasive and difficult elements to control is water. The tendency for water from rain or snow to seep into every available crack and crevice of a roof is a problem which has plagued many an unfortunate building owner. The damage resulting from such seepage may be severe, and often results in rotten wood, metal corrosion, damaged masonry, or damaged plaster or plasterboard. Costs of repairing these elements of a building damaged by water are generally high.
The problem of water infiltration is particularly acute at the intersection of an inclined roof slope and an upright wall, ridge, roof edge, vent, rake, eave, roof penetration, chimney, or other roof structure. Water tends to seep down along the structure or penetration, bypassing the roof, and finding its way into the roof. For example, and with reference to FIG. 1, in nearly every roofing application, there is a need to seal the joint and intersection (I) that is created between a generally planar roof (R1, R2) and any vertically extending structures such as dormers (not shown), chimneys (C), vents (V), and vertically projecting stories (S) that are elevated from any level of a lower roof (R1).
Conventional responses to such seepage include the adaptation of sections of a material impervious to water, known as “flashing” or “step flashing,” to prevent the infiltration of water and foreign objects into these intersections (I) or joints. Sections of flashing are typically sold as “flashing cards” that are generally flat or L-shaped in cross section.
Flashing is designed to manipulate the flow of water in a certain direction on the roof. Flashing also protects sections of a building where the shingles abut a wall or an edge. Commonly, flashing is used adjacent to chimneys (C). Flashing is also used when the building has more than one roof level. For example, as illustrated in FIG. 1, a building (B) may have a lower roof (R1) intersected by a projecting story (S) with an upper roof (R2). Flashing is needed at the intersection (I) where the shingles of the lower roof (R1) abut both the projecting story (S) and chimney (C) of the building. Methods of using and installing flashing are generally known and are described in U.S. Pat. Nos. 5,337,526 and 7,121,047, and U.S. Patent Application Publication No. US 2009/0178347, each of which are hereby incorporated by reference, in their entirety.
As illustrated generally in FIG. 2, flashing (F) is used to create a downwardly-projecting channel. Flashing (F) is fitted to the joints and angles of an intersection (I) before shingles, tiles, and/or other roofing material (S) is installed. A vertically projecting portion of the flashing (F) is attached and sealed to the vertical structure, for example, the chimney (C). The vertical portion may be nailed to the upright surface against which it abuts. A generally horizontal portion of the flashing (F) is attached to the roof (R) using roofing nails before the roofing material is applied. Additionally or alternatively, the flashing (F) may be attached to the roof by any suitable adhesive, including tar-based adhesives. A roofer alternates between securing a piece of flashing (F) to the roof and laying a shingle (S) or other roofing material over the horizontal portion of the flashing (F).
Flashing must be formed of a durable material that can withstand exposure to the environment for long periods of time. For example, the flashing is typically exposed to ultraviolet light from the Sun. As will be appreciated by one of skill in the art, exposure to UV light can damage some materials causing them to become brittle. Because of this, some materials and roofing components that are suitable for particular uses, such as roofing underlayment, cannot be used as flashing.
Conventional flashing is generally formed from sheet metal made of at least one of aluminum, galvanized steel, stainless steel, zinc, terne, lead, and copper. Flashing formed from these metal materials suffers from several disadvantages. Metals used to form conventional flashing are expensive, thereby increasing the cost of the flashing. Flashing made from these metals is also heavy resulting in significant transportation expenses and difficulty at a work site. Because flashing is often cut and formed into complex shapes during installation to match roofing connections, labor costs associated with installation of conventional flashing can be high. Additionally, some of these metals are rigid and difficult to work with and form, reducing efficiency during initial installation or replacement. Some of the metals used to form conventional flashing preclude the use of mechanical fasteners (such as nails and screws) and require crimping or the use of sealants. Moreover, some metals used for conventional flashing are highly reflective and detract from the aesthetic appearance of the roof. Although some types of flashing can be painted during installation to match the appearance building and roof, this requires additional time and material expenditures.
Conventional flashing also has a limited service life due to exposure to the elements and contact with other building materials. For example, metal flashing can be damaged through contact with green lumber, masonry, cement (which can each have high moisture levels), and treated lumber (due to chemicals used to treat the lumber that can react with the metal of the flashing).
Contact between conventional sheet metal flashing and fasteners made of a different metal can also result in a galvanic action that can corrode the flashing or the fastener and cause leaks. Unfortunately, conventional flashing and fasteners are produced using a range of materials that will have a galvanic interaction with each other. For example, fasteners made of metals which may be considered as non-reactive (for example, zinc and galvanized steel) will have a galvanic reaction with other metals frequently used in conventional flashing, such as tin, copper, steel, and stainless steel. Many individuals who install or repair roofs are not able to visually identify materials used to produce conventional flashing or know which materials are incompatible due to the risk of galvanic interaction. Compounding this problem, packaging of conventional flashing and other roofing materials that may provide warnings about galvanic interaction, identify the chemical makeup of the conventional flashing, or that provides warnings about detrimental material interactions is frequently not available to individuals installing or repairing roofs due to removal of packaging. Accordingly, even if packaging of conventional flashing were to provide warnings of galvanic reaction, because of the difficulty of identifying the material composition of other roofing materials and fixtures, it is unlikely that an individual installing a roof could be able to identify materials that are likely to galvanically react with the conventional flashing.
Some sheet metals used to form conventional flashing are coated with sealants to prevent corrosion of the metal. However, when the flashing is formed, the sheet metal is cut leaving edges that are uncoated and subject to corrosion. Further, when flashing is cut to form complex shapes by workers at a job site, the cut edges are also uncoated and a source of corrosion.
Finally, flashing made of lead is toxic and requires special handling techniques.
Accordingly, there is a need for a step flashing that is made of a durable, pliable, inexpensive, and lightweight material that is non-toxic and that improves efficiency of installation through reduced time required for installation and that is easy to work with in the field.